Apparatus for processing hexanitrostilbene

ABSTRACT

AN IMPROVED APPARATUS IS PROVIDED FOR PROCESSING THE EXPLOSIVE KNOWN AS HEXANITROSTILBENE (HNS) FROM A FORM KNOWN AS HNS-I INTO A FORM KNOWN AS HNS-II, TO PROVIDE A REFINED PRODUCT WITH A UNIQUE CRYSTAL FORM SO AS TO FACILITATE HANDLING OF THE MATERIAL. THE APPARATUS OF THE INVENTION USES AN IMPROVED EXTRACTION TECHNIQUE INVOLVING THE USE OF A SOLUTION OF ACETONITRILE IN WHICH HNS-I IS SOLUBLE AND XYLENE IN WHICH HNS IS INSOLUBEL FOR REFINING THE HNS-I INTO AN IMPROVED TYPE OF HNS-II.

1974 L. J. SYROP 3,832,142

APPARATUS FOR PROCESSING HEXANITROSTILBENE Original Filed Oct. 2, 1970 v 2 Sheets-Sheet 1 .feree/r Arie/1M7 F/df flea/f "1.--? M4 ne/A'c Man/Z #31:: 5,,

Aug. 27, 1974 L. J. SYROP 3,

APPARATUS FOR PROCESSING HEXANITROSTILBENE Original Filed Oct. 2, 1976 2 Sheets-Sheet P,

' -.L'ao/arrf (all/ell!!! 13.9 Cao/an/ .fexzfar 144 Pena/ a United States Patent use]. 23412.6 s 1 Claim ABSTRACT OF THE DISCLOSURE An improved apparatus is provided for processing the explosive knownas hexanitrostilbene (HNS) from a form known as HNS-I into a form known as HNSII, to provide a refined product with a unique crystal form so as to facilitate handling of the material. The apparatus of the invention uses an improved extraction technique involving the use of a solution of acetonitrile in which HNS-I is soluble and xylene in which HNS is insoluble for refining the HNS-I into an improved type of HNSII.

This application is a division of Application Ser. No. 77,653, filed Oct. 2, 1970 in the name of Leroy J. Syrop, which has ,now issued as Pat. No. 3,699,176.

BACKGROUND OF THE INVENTION Hexanitro'stilbene (HNS) was first produced at the Naval Ordnance Laboratory to meet a requirement for a heat resistant explosive. Subsequent research revealed that HNSpossesses other properties which are superior to similar types of explosives and which have resulted in-HNS being used for more general applications, even where'heat resistance is not a critical factor.

' Among the desirable features of HNS is the fact that it demonstrates acceptable performance in a temperature range extending, for example, from 320 to +525 0., which atests to the heat resistance properties of the material. In addition, HNS has been found to be relatively insensitive to electrostatic discharge, to be less sensitive to impact than tetryl, and to be radiation resistant. All the foregoing properties have led to the general acceptance of HNS as a superior material for explosive purposes. f

The apparatus of the present invention is intended to produce on' an eflicient and high'yield commercial scale large quantities OfHNSJI from HNS-I by an improved recrystallization process. The HNSII produced by the process and apparatusof the invention has controllable and predictable bulk densities of, for example, 0.5 to 1.0

:grams'per cubic centimeter. The process produces at the higher densities an extremely pure and free-flowing crystalline HNSII material having a unique grain structure.

denser, coarser and larger crystal than the HNSII pro- ;duced by theprior art methods, and has crystals of uniform'shape and of a generally orthorombic configura- "B'a'sically the process of the application Ser. No.

77,653 serves to transform HNS-I into an improved form of HNS II in which the crystal shape is changed, as mentioned above, so as to improve the handling characteristics of the resulting material. However, the HNSII produced by'the processalso has certain ancillary features in that it" is purer than the original HNS-I and can be compressed to a denser mass per unit volume so 3,832,142 Patented Aug. 27, 1974 as to provide a more powerful explosive and one with dilferent sensitivity to detonation, as compared with the original HNS-I.

In a prior art process for converting HNSI into HNSII, an extraction method was used involving acetonitrile which is a solvent insofar as HNS-I is concerned, and toluene which is a nonsolvent to HNS-I. Inthe practice of the prior art process, both the liquid acetonitrile and the liquid toluene are placed in av flask and the flask is heated. Since the boiling point of acetonitrile (81 C.) is lower than the boiling point of toluene C.), the acetonitrile boils first. The resulting acetonitrile vapor is caused to pass up to a condenser, and the condensed acetonitrile is passed through a quantity of HNS-I. The resulting solution of HNS-I, dissolved in the acetonitrile condensate, passes down into the flask, in which the toluene causes HNS-II to precipitate out of the solution. The aforesaid prior art process continues until all the available HNS-I has been dissolved and precipitated out as HNS-II.

However, the prior art process described in the preceding paragraph has certain inherent drawbacks. In the first place, the boiling points of the acetonitrile and toluene are sufliciently close together so that an appreciable amount of toluene vapor is produced during the process and is condensed along with the acetonitrile vapor. Therefore, the condensate passing through the HNS-I contains substantial amounts of toluene which inhibits the dissolution of the HNS-I into the acetonitrile condensate.

The aforesaid condition is aggravated in the prior art process by the fact that toluene and acetonitrile form an azeotrope with a boiling point lower than either the acetonitrile or the toluene. The resulting azeotrope results in further significant amounts of toluene appearing in the resulting vapor and in the subsequent condensate.

The foregoing factors result in low efliciency in the prior art process such that it is incapable of providing significant yield of HNS-II, or of operating on an efficient or economically feasible commercial basis. The process of the application Ser. No. 77,653 overcomes the deficiency of the prior art process by using a nonsolvent in the extraction process which has a boiling point materially above the boiling point of the solvent, and one which will not form an azeotrope with the solvent.

In the embodiment of the process to be described herein, the xylene in either its ortho, meta, or para form, or mixtures of all three forms, is used in conjunction with acetonitrile, the xylene replacing the toluene. The xylene has an advantage over the toluene in that its boiling point is about C. which represents a substantial displacement above the boiling point of the acetonitrile; and also in that the xylene does not form an azeotrope with the acetonitrile.

BRIEF- DESCRIPTION OF THE DRAWINGS FIG. 1 isa schematic illustration of appropriate apparatus in which the process of the application Ser. No. 77,653 may be carried out;

FIG. 2 is a side sectional view of improved apparatus constructed in accordance with the present invention for carrying out the process of the invention; and

FIG. 3 is a fragmentary showing of one of the components of the apparatus of FIG. 2, rotated 45 about its vertical axis as compared with the showing in 2.

DETAILED DESCRIPTION OF THE PROCESS AND APPARATUS OF THE INVENTION In the practice of the process of the'application Ser. No. 77,653, liquid xylene in either its ortho, meta or para form, or mixtures of all three forms, and liquid acetonitrile are placed in a flask, and the flask is heated to the boiling point of the acetonitrile so as to vaporize the acetonitrile. The resulting acetonitrile vapor is subsequently condensed, and passed down through a quantity of HNS-I. The resulting solution of HNS-I is dissolved in the acetonitrile condensate is returned to the original flask to precipitate the HNS-II out of the solution. The process is continued until all of the available HNS-I has been dissolved and subsequently precipitated as HNSII in the original flask.

One simple form of apparatus for carrying out the process is shown in FIG. 1. The apparatus shown in FIG. 1 includes, for example, a flask 10 which may be a 12 liter size. The flask 10 is supported in an appropriate heating mantle 12 which may be electrically energized. A magnetic stirrer is provided under the heating mantle and under the flask 10, to maintain the contents of the flask in an agitated condition. An extractor housing 16 is supported in the neck of the flask 10, the extractor housing surrounding an internal screen cup 18, and including a condenser 20 and a neck 22. A stopper 24 is inserted in the upper end of the neck 22.

In the practice of the process, the screen cup 18 is placed in the extractor housing, as shown in FIG. 1. The flask 10 has a further neck 30 which is closed by a stopper 32. The screen cup is filled with HNS-I material through the neck 22 by removing the stopper 24. Then, in the practice of a specific example of the process of the invention, 50 grams HNS-II seed are placed in the flask 10 through the neck 30 by removing the stopper 32. Three liters of acetonitrile and 5 liters of xylene (either ortho, meta, or para, or mixtures thereof) are inserted into the flask through the neck 30. The stopper 32 is then replaced. The magnetic stirrer 14 is activated, and a coolant, such as water is passed through the condenser 20. The heating mantle 12 is then energized, and observed until the system reaches steady state conditions.

The aforesaid process is continued for 12-30 hours, or until all the HNS-I in the cup 18 has been dissolved. The heating mantle 12 is then de-energized, and the solutions in the flask 10 allowed to cool to ambient temperatures. The magnetic stirrer 14 is activated during this interval, since it is important for vigorous stirring to continue throughout the entire cooling process.

The cooled solution may then be removed from the flask 10 through the neck 30 and filtered, for example, in a Biichner funnel. This results in a liberating of the HNS-II. The liberated HNS-JI is washed thoroughly, for example, in acetone, and then filtered. The resulting product is placed in drying pans and permitted to dry at temperatures in excess, for example, 100 C. for 8 hours. The resulting HNS-II is found to have all the characteristics described above, which provides for a pure product, and one which may more easily be handled than the original HNS-I.

Improved apparatus constructed in accordance with the invention is shown in FIGS. 2 and 3. As mentioned above, FIG. 2 is a side sectional view of the apparatus, and FIG. 3 is a view, partly in section, of the flask portion rotated 45 about its vertical axis, as compared with the view of FIG. 2.

The apparatus shown in FIGS. 2 and 3 is supported by appropriate bracket means (not shown). The apparatus includes a flask 100 which may have a capacity, for example, of 22 liters. The flask 100 has an upper neck and lower neck. The lower neck of the flask is supported in the neck of a receiver 102. The receiver 102 is surrounded, for example, by a jacket 104 through. which a suitable coolant, such as water is circulated. An outlet line 106 is provided at the bottom of the receiver 102, and the solution in the receiver may be removed by opening an appropriate stop cock 108;

The solution in the flask 100 is heated by means, for example, of a plurality of immersion heaters 110 which are inserted into the flask through appropriate necks disposed around the upper portion thereof. In a constructed embodiment, four evenly spaced heaters" are used, each having a power capability of 2 kilowatts. The heaters used in the constructed embodiment are formed of quartz, with a diameter of 1 inches, and a length of 19 inches.

A fractionating column 112 is inserted into the upper neck of the flask 100. The fractionating column includes a plurality of perforated plates 114 which serve as condensing surfaces for any vapor ofthe unwanted xylene. This causes the xylene to condense, so that the-fractionating column serves to inhibit the xylene vapor from rising into the extractor 116, the extractor being supported above the fractionating column 112. The fractio'nating column includes a silvered evacuated jacket 118,"which serves to insulate the column thermally from the external ambient temperature.

An appropriate stirrer is provided in the receiver 102, the stirrer 120 being operated, for example, by mechanical means insertedv into the receiver, or by appropriate external magnetic means. Likewise, a stirrer maybe inserted into the flask 100 through the neck 122 illustrated in FIG. 3. A temperature sensor 124 may be inserted into the flask 100, as shown in FIG. 3, through the neck 126.

In the operation of the apparatus of the invention, and as described above, the acetonitrile and xylene are inserted into the flask 100, and the solutions fill the flask and also the receiver 102. Then, the solution in the flask 100 is heated by the immersion heaters 110 so as to vaporize the acetonitrile, and to cause the acetonitrile vapor to rise through the fractionating column 112 and up through the extractor '116. The-xylene, which has a higher boiling point than the acetonitrile, and as described above, does not vaporize to any material extentfwithin the flask 100, and any xylene vapor that is generated is con;- densed and returned to the flask by the fractionating column 112, so that no measurable amount of xylene vapor reaches the extractor 1 16. g

The extractor 116 includes a series of concentric tubes. For example, the extractor includes a first tube-116a forming the outer wall of the extractor, anda second tube 116b is supported within the tube 116a by rod supports 130. A third inner tube 1 160 is supportedcoaxially within the tube 116b, by means, for example, of rod'supports such as the support 132. A condenser 136 is supported above the extractor 116, and an appropriate coolant, such as water, is circulated through the condenser. A temperature sensor 139 extends into the condenser, as shown.

A first filler neck 140 is provided in the housing 138, and the HNS-I is continuously inserted into the housing through that filler neck. The I-INS-I may be fed into" the apparatus through the filler neck by, appropriate automatic means, so that a predetermined amount of HNS-I is continuously fed into the system. Y A

A rotatably driven stirrer rod 142 extends down through the housing 138 and down into the-tube 116s of the extractor. The rod is supported,'for example, in' a Teflon bearing 144 at the upper end'of the tube -116c.- A stirrer 146 is mounted at the lower end of the rod 142, and between the open lower end of the tube 116a and the closed lower end of the tubular member 11617. p

In the operation of the apparatus, the acetonitrile vapor from the fractionating column 118 rises intothe'extractor 116 and through the annular space between the tube 116b and the tube 116a. The vapor then rises into the housing 138 where it is condensed by the condenser 136. The resulting condensate passes down into the extractor and over a drip ring 150. The HNS-I inserted into the filler neck 140 is dissolved into the condensate in accordance with the practice of the process as describedabove.

The condensate and dissolved HNS-I passes 'down through the annular space, between the tubes 116c-and 116b to the bottom of the tube =116b. The accumulating liquid is then forced up into the interior of the tube 116a and through an overflow orifice 18 0 into the space between the tubes 116a and 116b, and down through the fractionating column 118 into the flask 100. During this process, the stirrer 146 is turning in a direction so that its blades tend to force any solids in the liquid back up into the space between the tubes 1l'6b and 1160, so that the HNS-I may be fully dissolved in the condensate as it overflows through the orifice 1Q and down into the flask 100.

The rate of feed of the HNS-I, and temperatures are controlled so that a continuous action is achieved, and so that the acetonitrile condensate saturated with HNS-I is received into the flask 100. Appropriate filter means may be provided in the orifice E, to assure that no solid HNS-I passes down into the flask 100.

Then, as in the previously described apparatus, the xylene in the flask 100 precipitates HNS-H out of solution, and the precipitated HNS-II passes down into the receiver 102 where it is cooled. The cooled solution may periodically be removed by opening the stop cock valve 108, and filtering. Then, as before, the resulting I-INS-II is placed in drying pans and permitted to dry at the predetermined temperatures.

The apparatus of FIGS. 2 and 3 is advantageous in that it permits a continuous extraction process of HNS-II to be carried out, whereby the HNS-II is produced on a continuous and commercial basis within the receiver 102. The apparatus of the invention operates efliciently to yield high grade HNS-II on an economical commercial basis.

Although a particular embodiment of the apparatus of the invention has been described, modifications may be made. It is intended to cover all such modifications which fall within the scope of the invention in the following claim.

What is claimed is:

1. Apparatus for recrystallizing hexanitrostilbene from a Type-I to a Type-II consistency, said apparatus comprising: a flask for holding a solvent solution and a precipitant solution, said solvent solution having a lower boiling point than said precipitant solution; heating means for heating the solutions in said flask to cause said solvent solution to vaporize; a condenser for receiving the solvent vapor from said flask and serving to condense said vapor and to return the resulting condensate back to said flask; extractor means interposed between said flask and said condenser for accumulating the condensate, said extractor means comprising plurality of coaxial tubular members defining paths for the solvent vapor and for the solvent condensate and Type-I hexanitrostilbene dissolved therein, so as to provide a continuous vapor flow' upward through said extracto and a continuous flow of condensate and dissolved Type-I hexanitrostilbene down through said extractor; a iraetionating column interposed between said flask and said extractor means and serving to condense any vapor of the aforesaid precipitant solution in said flask which; may be evolved by heating means and for returning theresultant precipitant solution condensate to said flask; means for continuously introducing the Type-I hexanitrostil-bene into said extractor for causing the Type-I hexanitrostilbene to be dissolved in said condensate accumulated in said extractor before said cone densate is returned to said flask, said precipitant solution in said flask precipitating Type-II hexanitrolstilbene from the condensate returned to the flask; and receiver means disposed under said flask and established at a temperature lower than the temperature in said flask for receiving the Type-II hexanitrolstilbene precipitated by the aforesaid precipitant solution.

References Cited UNITED STATES PATENTS 1,648,224 1/1927 Hall 23-2126 5 3,423,192 1/1969 Sncwer 23-2126 s 3,053,846 9/1962 Varcoe 23-272.6 S 2,095,056 10/1937 Clough 23272.6S 1,794,874 3/1931 Trescott 23272.6 s 339,201 4/1886 Merz 23-272.6 s

FOREIGN PATENTS 839,116 1952 Germany 202187 NORMAN YUDKOFF, Primary Examiner S. J. EMERY, Assistant Examiner U.S. Cl. X.R. 202-169 

